The generation of electrical energy has long been practiced. Generation can be, for example, by coal-fired or nuclear-powered power plants, typically using steam turbines. Hydroelectric generation using dammed up water, large internal combustion engines driving generators, wind generators, photovoltaic electric generation, portable generators and the like are also used. Chemical reactions may also be used to generate electricity or electric current. Each type of generator has its advantages and disadvantages. For example, steam generation is usually accomplished in very large, very heavy equipment particularly with regard to the generator and the steam turbine that drives the generator. Electrical generation via steam turbines is typically not portable. Internal combustion engines likewise, to be efficient, are also very large and are typically diesel powered and are prone to vibrating. These too are typically not easily portable. There are portable generators that are small but tend to be relatively inefficient. Generators using internal combustion engines are typically limited to a single type of fuel such as diesel fuel, gasoline, gasoline/alcohol mixtures, or propane. Some stationary units use natural gas. Additionally, generator devices typically have a low power output per unit of volume. For example, a portable generator could have an output of less than about 2 kw/ft3 (based on the volume of alternator, engine and drive train)
While such generating systems are effective for producing electric current, they have their drawbacks, some of which were discussed above. Some of the drawbacks have been improved upon by using a Stirling engine to run an alternator forming a generator. An example of a Stirling engine/alternator generator set which utilizes a free piston-style Stirling engine to effect relative movement between magnets and coils in an alternator to generate electricity can be found in the prior art listed in U.S. Pat. No. 6,658,862. A Stirling engine utilizes external combustion to provide the energy to operate the engine and its coupled driven members. Problems associated with a piston-style engine are the friction between the pistons and cylinder walls, leakage of gas through the piston-cylinder wall gaps, the presence of moving mechanical parts at high temperature, and the inability to produce multiphase electricity, for example, three phase electricity, from the generator without additional equipment to convert single phase to multiphase electricity. The benefits of some types of Stirling engines, e.g. free-piston Stirling engines, are their simplicity due to the elimination of or the reduction in the number of moving components while maintaining high efficiency. A typical internal combustion engine is a highly complex mechanical system and has an efficiency of approximately 25% which desirably needs to be improved upon. It would also be desirable to provide a generator system using an external combustion energy source that can utilize a variety of combustible materials as a source of heat energy, or other non-combustion sources of heat energy such as geothermal energy, as opposed to specific fuel requirements for an internal combustion engine. However, to date, attempts at using Stirling engines for the production of electricity have not been successful particularly when it is desired to generate multiphase electric current without conversion.
Another problem with the use of internal combustion engines used in portable generators or fixed generators is that they have a tendency to vibrate and produce noise, both at the exhaust and in their normal vibrations from moving parts. As mentioned above, such engines are fuel specific, mechanically complex, and they have a significant amount of friction associated with their moving components resulting in inefficiencies.
It would thus be desirable, to provide a vibrationally-balanced Stirling energy conversion system that can be used to generate electric current utilizing external combustion or other external energy sources to provide a source of thermal energy. It would also be desirable to provide an electric current generator system that utilizes a Stirling engine to provide the motive driving energy for an alternator, and that the generator system be configured for multiphase electric current output without the need for conversion equipment. Alternatively, the system may be operated in reverse to function as a refrigerator or heat pump.